New Haven — Michael Thomas, the former Mashantucket Pequot tribal chairman, was sentenced Tuesday to 18 months in federal prison for embezzling more than $100,000 from the tribe that owns Foxwoods Resort Casino.

U.S. District Judge Janet Bond Arterton also ordered Thomas to serve three years of supervised release and to make restitution to the tribe.

Thomas, 45, has to surrender Jan. 14 to U.S. marshals.

Departing from sentencing guidelines that call for a prison term of 21 to 27 months, Arterton said she sought to strike a balance with Thomas' history of good deeds and advocacy for the tribe. But she said it was important to impose a sentence that reflected the seriousness of the crime.

A jury had found Thomas guilty in July on all three counts of an indictment charging him with misusing a tribe-issued American Express card to pay for personal expenses from October 2007 to September 2009. Most of the credit card charges were for transportation Thomas arranged for his ailing mother, who traveled to and from her Mashantucket home to a dialysis center in New London.

Thomas' public defender, Paul Thomas, said the tribe typically provided such a service for its "sick, elderly members" and would have done so for his client's mother had he requested it.

Paul Thomas and Michael Thomas are not related.

"This is not at all a classic case of corruption," Paul Thomas said. "Mr. Thomas had no intent to steal from the tribe or harm the tribe."

He called for a sentence of probation, a period of home detention in which his client could work and do community service. "Prison time would impede restitution," the attorney said.

Assistant U.S. Attorney Christopher Mattei, the lead prosecutor in the case, objected to Paul Thomas' characterization of his client's conduct, saying Michael Thomas was no different from any other public official who knowingly abused his office.

Michael Thomas addressed the judge, saying he accepted responsibility for "my actions and my inactions." He said he had told the tribal council the same thing on several occasions and had asked the council to tell him how much he owed the tribe. He said the tribe never told him.

"I have not skirted my responsibility," he said.

Thomas said the council removed him as chairman in 2009, locking him out of his office and prohibiting him from retrieving records. His removal, which was unrelated to his misuse of his tribal credit card, came after he had pledged to put funding for tribal government and payments to tribal members ahead of the tribe's financial obligations.

Arterton said the tribe knew or had the means to know that Michael Thomas' conduct involved theft and that it was not clear that all the responsibility for the theft should be directed at Thomas.

She drew a parallel between Thomas' conduct and that of a former New York City comptroller who was convicted of directing state employees to care for his ailing wife. In 2007, Alan Hevesi was ordered to pay a fine and was banned from holding elective office.

Nearly 20 tribal and family members attended the sentencing in a show of support for Michael Thomas. Other supporters had written to the court on his behalf, including former U.S. Rep. Patrick Kennedy of Rhode Island.

Rodney Butler, the current tribal chairman, wrote that Thomas was deserving of some consideration.

Arterton scheduled a hearing next month at which the sides will decide on the amount of restitution Thomas will be required to pay the tribe. The government contends he owes more than $120,000, while Thomas put the figure at about $100,000.

During discussion of Thomas' misuse of the credit card to pay for his mother's medical transportation and for the benefit of others, Arterton asked the prosecutor whether there was a "Robin Hood" aspect to Thomas' crimes.